Two explosions tore through the finish line of the Boston Marathon Monday within 30 seconds of each other, leaving three people dead and hundreds injured. The tragedy is being handled as an act of terror, according to the White House, and a person of interest is reportedly being detained at a hospital.

But that information doesn’t quell the conspiracy theorists on social media. Here are the top conspiracy theories swirling about the Boston Marathon bombings.

1. False Flag

Alex Jones, a radio host and the country's preeminent conspiracy theorist, suggests the attacks were a "false flag" operation devised by the government with the goal of ultimately expanding the Transportation Security Administration's reach to sporting events.

Our hearts go out to those that are hurt or killed #Boston marathon - but this thing stinks to high heaven #falseflag

2. Mystery Man on Roof

Dan Lampariello, a spectator at the race, snapped a photo of the second bomb exploding, and unintentionally captured the silhouette of a man standing on the roof of a building right above the blast. The photo quickly went viral.

Police reportedly cracked down on rooftop parties along the marathon route, leaving Twitter users stumped as to why someone would be up there.

"Who's the guy on the roof?" one Twitter user asked. "He's not reacting to the detonation."

"The picture of the guy on the roof overlooking the second explosion is the spookiest thing I have ever seen," another wrote.

4. The Facebook Page

Screenshots of a Facebook page started floating around Monday shortly after the bombings. The page, which was reportedly created two days prior and has since been deleted, was a memorial page with the title, "Thoughts Go out To All Those Involved In The Boston Explosions." But how could a memorial page be set up before the bombings occurred?

Twitter users also added to this theory by pointing out that police reportedly told people at the marathon to "be calm" before the bombs even went off, signifying that the government and police were somehow in on it.

The deadly blasts that shook the finish line Monday at the Boston Marathon have sparked a handful of conspiracy theories, with some speculating that the attacks were the work of far-right extremists or a mysterious man on a roof.